ABSTRACT This revised application requests funds to purchase an ABSciex 5500 triple quadrupole mass spectrometer and HPLC system (Shimadzu UPLC with a multiwell plate handling/rack changing autosampler) and workstation computer. This instrument is needed to augment services currently provided by an ABSciex 4000 Q-TRAP system that was purchased in 2007 with funds provided by an NIH S10 award (S10 RR024598) and has been in continuous service for the past 9 years as a mainstay of the University of Kentucky Small Molecule Mass Spectrometry Core Laboratory (services provided to 42 unique investigators and data generated for 90 peer reviewed publications). The requested instrument offers moderate improvements in speed, sensitivity and robustness over the 4000 series instrument and the UPLC system and rack changing/multiwell plate autosampler provide further improvements in sensitivity and sample throughput. This is an institution-wide facility core with permanent technical staff and faculty and administrative oversight necessary to ensure productive and financially sustainable operation. The core facility is directed by the PI of this application, Dr Morris. During this time, the instrument has provided services to NIH funded researchers engaged in Cancer, Cardiovascular, Metabolic Disease, Drug Discovery, Nutrition and Environmental Toxicology research both at the University of Kentucky and at several other regional and national institutions. The instrument has been used to generate data that were reported in 104 publications, to provide services that were critical to successful applications for multiple personal and programmatic research awards and to provide training in biomedical applications of mass spectrometry to students and fellows. The requested instrument is required to maintain the overall research capacity of the facility (~12,000 services/year) which is currently dependent on use of a second ABSciex 4000 Q-Trap that was purchased in 2009 with a supplement to one of Dr Morris's personal research grants. This instrument includes an ABSciex Flashquant vacuum MALDI source which enables its use for multiwell plate format enzyme assays and its use in this configuration for personal research purposes limits its availability for core facility services. The Major Users conduct NIH sponsored research in Lipid Metabolism and Signaling, Nutrition and Environmental Toxicology and Drug Discovery and Natural Products. Minor Users with relevant interests and qualifying support are also included. The facility core employs two analytical chemists with broad experience in mass spectrometry that will be responsible for day to day oversight, upkeep and operation of the requested instrument. Dr Morris and staff have extensive track record of success in the development and application of mass spectrometry-based methods for biomedical research and the facility core is overseen by an advisory committee staffed by individuals with appropriate and complementary expertise in analytical chemistry, mass spectrometry, data management and facility core oversight. Financial operation of the core adheres to federal cost accounting standards with a sustainable business plan underwritten by the College of Medicine and the Vice President for Research.